Aquatic herbicides

ABSTRACT

Application of a herbicidally effective amount of a substantially insoluble copper-containing compound to areas of water infested with undesirable aquatic plants so that the compound comes into contact with the plants and is held thereby, destroys said plants with minimal pollution of the water and toxicity to other forms of aquatic life.

United States Patent Robert W. Geiger;

Alfred M. Teten, both of Minneapolis; William G. Paterson, Roseviile, all of Minn. 82 1,161

Apr. 1, 1969 Jan. 11, 1972 Minnesota Mining and Manufacturing Company St. Paul, Minn.

inventors App]. No. Filed Patented Assignee AQUATIC HERBICIDES 12 Claims, No Drawings Field of Search 7 1/66, 67, 65

[56] References Cited UNITED STATES PATENTS 2,284,889 6/1942 Fischer 7 H67 2,734,028 2/1956 Domogalla 71/67 Primary Examiner.lames 0. Thomas, Jr. Attorney Kinney, Alexander, Sell, Steldt & Delahunt ABSTRACT: Application of a herbicidally effective amount of a substantially insoluble copper-containing compound to areas of water infested with undesirable aquatic plants so that the compound comes into contact with the plants and is held thereby, destroys said plants with minimal pollution of the water and toxicity to other forms of aquatic life.

AQUATIC HERBICIDES BACKGROUND OF THE INVENTION The invention relates to the use of substantially insoluble copper-containing compounds, especially malachite, scientifically named basic copper carbonate, in the control of Chara vulgaris, filamentous algae, and other aquatic plants.

lnland waters have become quite important as they are used for recreation, irrigation, fire protection, livestock, fish production, and many other related uses. These waters are becoming more subject to pollution with the growth of population, and thus, aquatic plant growth has become a serious problem. Especially troublesome plants are Chara vulgaris, filamentous algae, and vascular plants such as Ceratophyllum demersum, Elodea canadensis, and Najas guadalupensis.

Chara is a green alga having a skunk or garlic odor and a rather slick taste. Closely related to Chara, and as troublesome, is an algae called Nitella having a green color, a grassy odor and a bitter taste. Representative filamentous algae are Spirogyra, Zygnema, Oedogonium, Pithophora, and Cladophora. Not only are these algae noted for their odor and taste but they also cause slime, discoloration of water and corrosion of metal and concrete.

These unsightly, obnoxious plants grow both beneath and on the surface of the water. The algae have been troublesome to boaters, fishermen, and swimmers, are very unattractive in residential areas and create health hazards by infesting portable water supplies. Further, certain phankton algae in the water can be toxic to people or animals that come in contact with it by swimming in or drinking the water. Examples of other toxic algae are Anabaena and Aphanizomenon.

Various attempts have been made to subdue the growth of aquatic plants, especially algae, or destroy them. A compound commonly used at the present time is soluble copper sulfate. Copper sulfate, however, does not control aquatic plants to the extent desired. The compound is ineffective in controlling many aquatic plants such as Chara vulgaris, Cladophora and Nitella. To obtain effective control of some aquatic plants using copper sulfate, as well as other aquatic herbicides used presently, large amounts must be used to raise the copper concentration of the entire body of water to an effective dosage rate. At this effective dosage rate, with such large amounts being required, these compounds are generally toxic to desirable aquatic life such as fish and certain plants, particularly in soft water. Further, these compounds may be toxic or hazardous to the applicator and there is a large amount of water pollution resulting from their use. It has also been found that water-soluble compounds such as copper sulfate and alkaline algicides such as sodium arsenite and long chain alkylamine salts of endothall tend to be corrosive to pumping and spraying equipment used in applying the compounds to the infested water.

SUMMARY OF THE INVENTION According to the present invention, undesirable aquatic plants are destroyed by application of a herbicidally effective amount of a substantially insoluble copper-containing compound to the locus that is infested with these plants in a manner so that the compound comes in direct contact with the plants and rests on the plant surface or is held thereby.

Among the many substantially insoluble copper-containing compounds which have been found useful, the preferred are basic copper (ll) carbonate, copper (ll) bicarbonate, copper (I) oxide, copper (ll) benzoate, copper (II) hydroxide, copper (ll) oxide, copper (I) thiocyanate, copper (l) azide and copper (ll) azide. Copper azide is considered explosive but if kept wet in a slurry, is safe for use. Basic copper (ll) carbonate (hereinafter referred to as copper carbonate) is generally preferred as it is easily obtained, inexpensive, and very effectual. This material is essentially 100 percent CuCO Cu(OH) with slight traces of other metals and is commonly called malachite. Where the material is 2CuCO Cu(OH) it is commonly called azurite and may also be used. Although the compound has been used for the control of terrestrial fungi and, in conjunction with other materials, for the control of swimmers itch, by controlling snails carrying the infectionproducing parasite, to applicants knowledge insoluble coppercontaining compounds have never been used to control aquatic plants as described herein. In fact, hydrobiologists have stated that it is the formation of insoluble copper carbonate in the alkaline water that renders copper sulfate unusable in some cases as an algicide. See, for example, Domogalla et al., 15 Years of Algae Control, U.S. Trout News, March- April, 1963, pg. 8. It has been stated also, according to the above reference that the heavy copper carbonate precipitate in the water would be toxic to fish and also reduce fish food organisms in the bottom muds. Although the insoluble character of the compounds used in this invention suggests that they would be poor aquatic herbicides, it was found that the insoluble copper-containing compounds effectively controlled undesirable aquatic plants without having an adverse effect upon fish and other aquatic life.

The use of relatively insoluble copper compounds has proven to be nontoxic to desirable aquatic life and yet destructive to undesirable plants primarily because of the mechanism by which the compounds work. The copper-containing compounds, such as malachite, are in the form of wettable powders.

Compounds not inherently wettable may be made so by the addition of a wetting agent such as sodium dioctylsulfosuccinate. Other inert ingredients may also be added to modify the aquatic herbicide, these modifications being well known in the art. For example, for certain compounds it may be desirable to include a dust inhibitor such as glycerine.

When mixed with water, the slurry is sprayed on the surface of the water only in the area of infestation rather than underwater and, upon solubilizing, permeating the entire area, the latter being recommended for soluble algicides. As the compound settles through the water, it settles on or clings to the plant. At this point there is a very slow dissolution of copper ions into the previously copper-free area at the plant surface. As a small amount of copper ion is released, it is absorbed by the plant thus causing additional copper ions to be slowly released. This type of reaction is best described as the Le Chatelier principle of equilibrium. In accordance with that principle, the absorption of the copper by the plant creates a pressure on one side of the reaction which upsets the solubility equilibrium. Taking the copper ions out of solution by the plant causes the release of more copper ions into that area which in turn are absorbed causing the release of again more copper ions. This controlled release requires that only a small amount of the slightly soluble copper-containing compound need be used and demonstrates the importance of the copper compound being substantially insoluble. High concentrations of the copper ion need not be used and, therefore, do not exist in areas other than at the plant surface where the copper is absorbed. As a result, toxic effects on desirable organisms in the surrounding area are avoided.

Due to the low solubility of the copper-containing compounds of this invention, which is below 50 mg. per liter, and to the resulting lower dosage required for control, the water is less polluted than when using algicides known in the prior art. This is an especially desirable result when the compounds are used in reservoirs which supply the water for a city. Other advantages are that the algae control may be localized to the treated area only and the compound does not lose its toxicant through absorption by bottom muds as do granular formulations employing soluble materials. The compounds of this invention are highly effective under a wide variety of aquatic conditions. The material is effective in water over a wide range of temperatures. It is further effective under varying conditions such as water clarity, hardness, total alkalinity, pH, and other parameters and is effective at essentially all growth stages of Chara and filamentous algae. Further, the material is noncorrosive to pumping equipment and mixing tanks and is safer to the applicator than soluble copper-containing compounds.

The substantially insoluble copper-containing compound Compounds. Localized treatment in accordance with this inuseful in the present invention,asheretofore described, h ve a vention allows destruction of unwanted aquatic plants with solubility in pure water up to about 50 mg. per liter, on the y small concentrations pp basis of dissolved copper ion. The preferred solubility range The following hohhmitthg examples will serve to further for these compounds is from about 0.001 to 1.0 mg. per liter 5 JEEtLE EL EjEYeD LK-MM. copper ion which is a safe range for desirable aquatic life. EXAMPLE] Copper compounds with a solubility greater than 50 mg. per A square l.0-acre test plot was marked off with stakes near liter will probably dissolve before they reach the plant sought the shore of a lake which was infested with Chara (Chara vulto be destroyed. An early solubilization of these compounds garis) and filamentous algae. The lake bottom was silt. Five results in effects as those observed with copper sulfate and ob- Pounds of finely divided (about 100 m hasle pp viates those advantages described with using insoluble copper carbonate were mixed h 30 gallons of water and the resultcompounds having localized activity at the plant surface, such 8 slurry was sprayed uhltotmly Over the e of the s as reduced toxicity to fish, reduced pollution and the use of P by means ofa mechanical Sprayer- The Particles of basic small amounts. The compounds should be in a finely divided copper carbonatevsemed through the water and l rest form so that intimate contact can be made with the undesiraon the filamentous e The i temperatmie ble Plant and increase the emcacy of the absorption of the was 72 F. Within l0 days, an obvious condition of chlorosls copper by the plant. For the purposes of the invention, the (grew lose colgr g i becmlne l z gy copper compounds are ground to about 0.01 to 1,000 microns apparent m the Chara an t e I amemous a gae a tegrated. The Chara had a moribund appearance and m dlameter and to I00 mlcrons preferred Granular gradually disappeared from the test area over the next several material sinks to l bottom and would not be desirable for weeks. The Chara and algae in the areas surrounding the test the purposes of the invention. plot remained green and healthy.

The substantially insoluble copper compounds of the present invention have crystalline densities of well in excess of EXAMPLE II the density of water so that these materials will settle readily A 35-foot perimeter of a small lake was treated at a dosage therein. The sedimentation characteristics of these comrate of 20 pounds per acre of similarly divided basic copper pounds were determined by dispersing 5 g. of the material in carbonate. The treated area amounted to 2.3 acres and was 45 g, f at nd pouring h slurry i a 3%-i h di very heavily infested with a lush growth of Chara and filamentube which has a 65 -inch column of water from the surface tolls s The lake had a sandy bottom and was subject to a to the monitoring section. A light source and photomultiplier slight watel'flow from canals at PP ends of the lake- The canals led to adjacent lakes which were part of an extensive system of fresh water lakes and canals. The adjacent lakes were similarly infested. The lake perimeter was treated in several stages by mixing the 6.5 pounds of basic copper carbonate with 100 gallons water in a ISO-gallon fiber glass tank equipped with a mechanical agitator. The resulting green slurry was sprayed uniformly over the surface of the treated area. The water temperature was 82 F. Within a week following treatment, the treated vegetation acquired a pale and sickly tube were used to count the particles as they passed the monitoring section. Sedimentation was the greatest in about 8 minutes and most of the material settled 20 minutes after application. Results indicate that most of the particles settle on the plant surface in 8 to 20 minutes and are not dispersed throughout a large area. This is important as only the amount of copper that is required to control algae in a given area is needed rather than saturating a whole lake or pond with the 40 material. Toxicity to desirable species is minimal and cost appearance, and it gradually disintegrated and disappeared greatly f from the treated area. Virtually complete control of Chara water Solublhty the copper (fompounds of the present was observed after 3 months. The adjacent lakes remained invention was determined by adding them to l-gallon water fested' samples in amounts such that the copper concentration would The average water depth in the treated area was 4 f t so be 5 8- P the! if the material dissolvedp that the amount of copper in the treated area was the same as when testing malachite, the water samples were stirred for it i were t d with 4 m copper sulfate pentahydrate four hours and then analyzed for copper. The copper content (equivalent to l p.p.m. copper ion). in the present example, in distilled water was 0.007 mg. per liter while in distilled however, the basic copper carbonate is very sparingly soluble water with the malachite included, it was 0.020 mg. per liter. in water, and there is an extremely low level (about 0.02 Similarly the copper content of ordinary like water was 0.030 p.p.m.) of copper ion present in the water. The present parts per million while lake water with malachite has a copper method of treatment offers a big margin of safety to fish comcontent of 0090 parts per million. These results indicate that pared with treatments using Soluble pp compoundsthe malachite or basic copper carbonate is substantially in- EXAMPLE m soluble in distilled water or lake water thus offering a large margin of safety to other marine life.

The compound may be used in a range of one-half to 400 pounds per acre but preferably something less than 5 to 20 pounds per acre is used. For algae, 0.025 to 5 parts copper per in a lake infested with Chara (Chara vulgaris), Nitella (Nitella spp.) and filamentous algae, an area measuring 375 feet along the shore by 100 feet out into the lake (0.85 acre) was treated as described in the previous examples with basic copper carbonate at a dosage rate of 12 pounds per acre.

mlmon parts be used treatment about to Within six days after treatment, the vegetation in the treated parts per mmlon bemg preferred For Vascular plants sl lch area had become colorless and mushy and in another l2 days as cemtophynum from about to 200 Parts Per mlmon the area was essentially free of vegetation. The control lasted may be used- These levels represent total coppe" However 5 at least 5 months, at which time the onset of cold weather the amount in solution is always much less the total made further observations meaningless. During the field trial, amount added because of the insoluble nature of the the areas surrounding the test plot remained infested with pounds. it is desirable to use as little copper-containing com- Chara, Nitella, and other forms of algae. pound as possible because of the toxicity problems previously Further examples are set out in the following table wherein noted, although toxicity is substantially reduced with such basic copper carbonate wasused as thealgicide.

Weed control data Dosage m Example Body of Shoreline type and Cloud cover-wind, water temperature, Plot size, rate, Weeds or algae in Number Percent No. water lake bottom water clarity depth lbs./a. test of days control IV Lake Residential 025%; calm; above 70 F.; clear 0.85 a., 4 ft 12 gfigggg gggg' bj: jig

D Weed control data osage Example Body of Shoreline type and Cloud cover-wind,water temperature, Plot size, rate, Weeds or algae in Number Percent No. water lake bottom water clarity depth lbs/a. test of days control C. l a 15 am vu aria 90 V Lake. Residerlttlal; sand, 25%; calm; above 70 F.; clear 2.3 a., 4 it 20 a 60 98 grave Filamentous algae 3 :gg gliara vufgariap 25 90 VI o am vu gun's 25 75 Lake. Rgsgzregtllagliand, 25 75%, 0-19 M.P.H., 66 F., turbld.. 1 a., 4.5 It"... 20 chum Wham 25 80 40 glllmru vullgaris 25 80 VII a 1 30 am an gun's 28 80 Lake. Forest silt 25 15%, a M.P.H., 6s I clear 1 a., 5 ft 5 Ohm m H 28 50 Chara vu gun's- 27 100 VIII Lake Forest silt 025%; 5-10 M.P.H.; 65 F.; clear 1 a., 5 it 30 Chara vulaaris" 27 1 16 Chara vulgaria 27 90 IX Lake.. Forest silt 2.3 a., 4-& ft 20 Chara vuluaris" 32 100 EXAMPLE X Duplicate samples of Coontail (Ceratophyllum demersum) which were growing vigorously in l-gallon jars filled with water were treated by adding to the jars an aqueous slurry containing 0.007 grams of basic copper carbonate which is equivalent to a copper concentration of 1.0 part per million if all of the material would have dissolved. Some discoloration of the plant was obvious within 12 hours and there was extensive defoliation within 24 hours. Five days after treatment the stems had separated from the nodes an extensive discoloration of the plants was obvious. An untreated control plant showed new growth during the same period.

EXAMPLE Xi Using the procedures of example 1, essentially similar results are obtained by using copper (ll) azide in place of basic:

copper carbonate.

EXAMPLE Xll A small oval 0.6 acre pond, which was infested with a' growth of Chara vulgaris and filamentous algae, was treated as described in previous examples with l.2 lbs. of powdered copper (l) oxide which has been premixed with l0 gal. of water. The average depth of the pond was 2.5 feet, so that the dosage of copper (l) oxide was equivalent to a copper concen- EXAMPLE Xlll A rectangular test area, approximately 100 feet wide by 400 feet long with an average depth of 3.5 feet, was marked off with stakes along the shore of a very large pond which was infested with a growth of Ceratophyllum demersum, Hydrilla verlicillata, and filamentous algae. An aqueous suspension containing 40 pounds of copper (ll) hydroxide in 40 gal. water was sprayed evenly over the surface of the staked area. The particles of copper (ll) hydroxide settled through the water and came to rest on the weeds and algae. A general condition of chlorosis was apparent in all the treated plants within three days of the herbicide application, and the weeds and algae gradually disintegrated and disappeared during the next several weeks. The weeds and algae in the areas surrounding the trial area remained in a healthy condition.

What is claimed is:

1. A method of destroying undesirable aquatic plants in lakes, ponds, waterways, and the like, comprising applying only to the area infested with said plants, an herbicidally effective amount of a substantially insoluble copper-containing compound selected from the group consisting of copper (ll) carbonate, copper (l) oxide, copper (ll) oxide, copper (ll) benzoate, copper (ll) bicarbonate, copper (ll) hydroxide, copper (l) azide, and copper (ll) azide, said compound being in particulate form and only being effective when the particles contact said plants, said method substantially reducing the amount of copper compound in the surrounding aquatic environment thereby greatly minimizing the destruction of desirable aquatic life.

2. A method as recited in claim 1 wherein said copper-containing compound is basic copper (ll) carbonate.

3. A method as recited in claim 1 wherein said copper-containing compound is copper l) oxide.

4. A method as recited in claim I wherein said copper-containing compound is copper (ll) oxide.

5. A method as recited in claim 1 wherein said copper-containing compound is copper (ll) benzoate.

6. A method as recited in claim 1 wherein said copper-containing compound is copper (ll) bicarbonate.

' 7. A method as recited in claim I wherein said copper-containing compound is copper (ll) hydroxide.

8. A method as recited in claim 1 wherein said copper-containing compound is copper (l) azide.

9. A method as recited in claim 1 wherein said copper-containing compound is copper (ll) azicle.

10. A method of destroying undesirable aquatic plants comprising treating water containing such plants with a herbicidally effective amount of malachite having from 55.3 to 56.l percent by weight of copper, whereby said malachite settles through the water and rests on the plant, said malachite being substantially insoluble in water so that said copper goes into solution at the surface of the algae and is rapidly absorbed thereby.

ll. A method as recited in claim 10 wherein said herbicidally effective amount is from l to 40 pounds of said malachite per acre.

12. A method as recited in claim 1 wherein said copper-containing compound has a solubility in water of from about 0.00l to parts per million. 

2. A method as recited in claim 1 wherein said copper-containing compound is basic copper (II) carbonate.
 3. A method as recited in claim 1 wherein said copper-containing compound is copper (I) oxide.
 4. A method as recited in claim 1 wherein said copper-containing compound is copper (II) oxide.
 5. A method as recited in claim 1 wherein said copper-containing compound is copper (II) benzoate.
 6. A method as recited in claim 1 wherein said copper-containing compound is copper (II) bicarbonate.
 7. A method as recited in claim 1 wherein said copper-containing compound is copper (II) hydroxide.
 8. A method as recited in claim 1 wherein said copper-containing compound is copper (I) azide.
 9. A method as recited in claim 1 wherein said copper-containing compound is copper (II) azide.
 10. A method of destroying undesirable aquatic plants comprising treating water containing such plants with a herbicidally effective amount of malachite having from 55.3 to 56.1 percent by weight of copper, whereby said malachite settles through the water and rests on the plant, said malachite being substantially insoluble in water so that said copper goes into solution at the surface of the algae and is rapidly absorbed thereby.
 11. A method as recited in claim 10 wherein said herbicidally effective amount is from 1 to 40 pounds of said malachite per acre.
 12. A method as recited in claim 1 wherein said copper-containing compound has a solubility in water of from about 0.001 to 100 parts per million. 